Investigations on the influence of helminth parasites on vaccination of chickens against Newcastle disease virus under village conditions

Anthelmintic Activity of Saussurea costus (Falc.) Lipsch. Against Ascaridia galli, a Pathogenic Nematode in Poultry: In Vitro and In Vivo Studies

AIM OF THE STUDY

The growing resistance of helminth parasites to currently available commercial anthelmintic drugs, combined with apprehensions regarding detrimental chemical residues in livestock products, has sparked an interest in exploring medicinal plants as an alternative strategy for treating helminthiasis. As a result, this study was designed to investigate the anthelmintic activity of crude methanolic extracts (CME) of Saussurea costus root on Ascaridia.galli, a pathogenic nematode of poultry.

MATERIALS AND METHODS

In vitro, the anthelmintic effect of Saussurea costus root was evaluated in comparison to commercial anthelmintic, levamisole on the adult nematode parasites, A.galli using worm motility inhibition (WMI) test. The CME of S.costus was also evaluated for in vivo anthelmintic activity in chickens experimentally infected with Ascaridia galli. For the in vivo study, one hundred-day-old chickens were orally infected with embryonated eggs of A. galli worms. The efficacy of the plant extract as an anthelmintic was assessed through two tests: faecal egg count reduction (FECR) test and worm count reduction (WCR) test. The study investigated three distinct doses of plant extract under in vivo setup: 500 mg kg-1 body weight (bw), 1000 mg kg-1 bw, and 2000 mg kg-1 bw.

RESULTS

In vitro, all the tested concentrations of S.costus (25 mg/ml, 50 mg/ml, and 100 mg/ml) showed a significant (P < 0.001) anthelmintic effects on live adult A. galli worms in terms of inhibition of worm motility at different hours post-treatment. At the highest concentration of the extract, we observed worm motility inhibition of 100% at 24 h post-exposure. On day 14 post-treatment, all birds were slaughtered, and adult A. galli worms were subsequently retrieved from their small intestines. Birds treated with CME extract of S. costus root exhibited a significant (P < 0.001) reduction in faecal egg count. However, the administration of the extract at the dosage of 500 mg kg-1bw to the birds did not reveal any significant (P > 0.05) differences in the worm count compared to the negative control group. The CME of S. costus at a dose of 2000 mg kg-1bw showed the highest anthelmintic activity by inducing 83.10% FECR and 76.47% WCR.

CONCLUSION

In conclusion, the root extract of S. costus has a promising anthelmintic activity on A. galli as demonstrated by the results of the present experiment.

Evaluation of anthelmintic efficacy of ethanolic leaf extract of Juglans regia L. on Ascaridia galli: a comprehensive in vitro and in vivo study

Anthelmintic resistance in livestock animals has been spreading across the world in prevalence and severity. As a result, researchers are exploring alternative strategies to combat this issue, and one promising avenue is the utilization of medicinal plants. This study aims to investigate the anthelmintic efficacy of the crude ethanolic extract (CEE) derived from the leaves of Juglans regia against one of the most detrimental nematode parasites affecting poultry, namely Ascaridia galli (A. galli). For the in vitro studies, adult A. galli worms were collected from the naturally infected chickens and the efficacy of CEE was measured at the concentration of 25, 50, and 100 mg/ml using adult worm motility inhibition (WMI) assay. In addition, levamisole (0.55 mg/ml) was used as the positive control. Likewise, Phosphate buffered saline (PBS) was used as the negative control. For the in vivo studies, CEE of J.regia at the doses of 500, 1000, and 2000 mg/kg were evaluated in chickens experimentally infected with A. galli. The anthelmintic efficacy was monitored using faecal egg count reduction (FECR) and worm count reduction (WCR) assays. In vitro studies revealed significant (P < 0.001) anthelmintic effects of CEE of J.regia on the motility of A. galli worms at different hours post-exposure. At the concentration of 100 mg/ml, CEE resulted in 96.5% inhibition of worm motility at 24 h post-exposure. While the synthetic anthelmintic drug, levamisole caused the highest inhibition of worm motility (100%) at the same time period. The in vivo anthelmintic activity of CEE of J. regia demonstrated a maximum effect on day 14 post-treatment by inducing 67.28% FECR and 65.03% WCR. We observed no significant difference (P > 0.05) in worm counts between the negative control group and the chickens treated with CEE at the dosage of 500 mg/kg. Together, the results of the present study suggest that CEE of J. regia leaves possess anthelmintic properties and could be a potential source of novel anthelmintic compounds for controlling helminth parasites.

Prevalence and magnitude of gastrointestinal helminth infections in cage-free laying chickens in Australia

Helminth infections have been re-emerging with the growing popularity of free-range and floor-based chicken production systems. The aim of this study was to determine the prevalence and worm burdens of intestinal helminth infection in cage-free laying chickens in Australia. In an online survey about worm prevalence, a high proportion of respondents reported the detection of Ascaridia galli (77%), followed by tapeworms (69%) and caecal worms (Heterakis gallinarum) (62%), whereas fewer respondents (23%) reported the presence of hair worms (Capillaria spp.) in their flocks. Total worm recovery from 407 laying hens on four farms found that 92.1% of hens harboured one or more helminth parasite with a prevalence of 73 to 100% across farms. Mixed infections were common with 79% of hens harbouring two or more helminth species. The prevalence of nematode species H. gallinarum, A. galli and Capillaria spp. was 87, 82 and 35% respectively. Five cestode species were found with a low individual chicken prevalence (Raillietina tetragona 4.7%, Raillietina echinobothrida 3.2%, Raillietina cesticillus 5.2%, Choanotaenia infundibulum 4.4%, and Hymenolepis cantaniana 4.4%). The hens harboured an average of 71 worms with H. gallinarum having the highest mean burden (45.5 worms/hen) followed by A. galli (22.0 worms/hen), Capillaria spp. (2.7 worms/hen) and cestodes (0.8 worms/hen). The sex ratio (female:male worms) was 1.38:1 for A. galli, and 1.77:1 for H. gallinarum. There was a strong positive correlation between A. galli female worm count and excreta egg count (EECs) (r_s = 0.94, P < 0.0001) and also between total nematode worm count and EEC (r_s = 0.82, P < 0.0001) in individual hens. When investigating intestinal excreta (n = 10) and caecal excreta (n = 10) of 16 chicken flocks the prevalence of infection with ascarid worms in intestinal and caecal excreta was 71 and 78% respectively and 27% prevalence of Capillaria spp. in intestinal excreta with mean EECs of 407, 404, and 18 eggs/g of excreta (EPG), respectively. These results suggest that most chickens kept in free-range or floor production systems are infected with one or more helminth parasite species. Heavy worm infections would likely affect the production performance and welfare of birds with adverse economic impact. Strategic or tactical anthelmintic treatment with effective anthelmintic could reduce this impact.

Anthelmintic efficacy evaluation against different developmental stages of Ascaridia galli following individual or group administration in artificially trickle-infected chickens

The efficacy of commercially available anthelmintics against mature and immature stages (including ovicidal effects) of two Australian field isolates of Ascaridia galli was evaluated in two separate experiments. The anthelmintics tested were levamisole (LEV), piperazine (PIP) and flubendazole (FBZ) plus LEV-PIP. A total of 192 artificially trickle-infected young cockerels (96 birds per isolate) were randomized into sixteen experimental groups of 12 cockerels each (7 treatments and 1 untreated control per isolate). Chickens received label-recommended doses of LEV (28 mg/kg), PIP (100 mg/kg) or LEV-PIP co-administered at their full individual doses as a single oral dose or in group drinking water at recommended concentrations of 0.8 mg/ml or 2.5 mg/ml over eight hours for 1 and 2 days respectively and FLBZ (30 ppm) in the feed over 7 days. Anthelmintic efficacies were assessed by worm count reduction (WCR%) and excreta egg count reduction (EECR%) estimated by two methods. Ten days post treatment, all untreated control birds harboured mixed worm population of 10.1 and 12.3/bird for each isolate respectively which was significantly higher (P < 0.0001) than counts in all treatment groups. Luminal or histotrophic larvae comprised 50-57 % of the total worm count. For LEV, PIP and LEV-PIP, individual oral administration provided a somewhat higher efficacy than group medication in drinking water. EECR% values were inconsistent with WCR% and found to be only an indicator of efficacy against adult worms. All developmental stages of the two A. galli isolates were highly susceptible to FLBZ (100 %) followed by LEV-PIP (92.4-100 %) and LEV (87.7-100 %). PIP exhibited good efficacy against adult worms (92-97 %) but reduced efficacy against luminal (79-84 %) and histotrophic (61-72 %) larvae. Embryonation capacity of eggs recovered from worms expelled after treatment with LEV (47-54 %), PIP (44-54 %) or LEV-PIP (45-48 %) did not differ from those from untreated birds (50-51 %) whereas eggs from FLBZ treated worms had a significantly lower (P < 0.05) capacity to embryonate (≤ 2 %). Put together, our results demonstrate no evidence of resistance of the test A. galli isolates to the tested anthelmintics but a significant advantage of FLBZ, followed by LEV-PIP and LEV over PIP in the control of A. galli, specifically with regard to immature stages. A. galli worms expelled after treatment with LEV, PIP or their combination, but not FLBZ contain viable eggs. This has epidemiological implications and may also provide an option for isolating eggs from mature worms for A. galli propagation experiments without having to sacrifice birds.

Impact of Nematode Infections on Non-specific and Vaccine-Induced Humoral Immunity in Dual-Purpose or Layer-Type Chicken Genotypes

Nematode infections may induce immune-modulatory effects and influence host-immune responses to other pathogens. The aim of the study was to investigate whether a mixed nematode-infection influences non-specific and vaccine-induced humoral immunity against Newcastle Disease Virus (NDV), Infectious Bronchitis Virus (IBV), and Avian Metapneumovirus (AMPV) in already vaccinated hens of a dual-purpose (Lohmann Dual, LD) or a layer genotype (Lohmann Brown Plus; LB). Until 17 weeks-of-age, LD (n = 70) and LB (n = 109) hens were vaccinated against major bacterial and viral diseases and coccidiosis. At 24 weeks-of-age, the hens received either a placebo or an oral inoculation of 1,000 infectious eggs of A. galli and H. gallinarum. Plasma total immunoglobulin (Ig) isotypes (IgY, IgM, IgA) levels and vaccine-induced antibody titers against NDV, IBV, and AMPV were determined from 2 to 18 weeks post-infection (wpi). Infections had no suppressing effect on total Ig isotypes IgY, IgM, and IgA as well as on vaccine-induced antibody titers against NDV, IBV, and AMPV (P > 0.05). Overall, LB hens had higher levels of IgY, IgM, and IgA than those of LD hens (P < 0.05). There were no differences between IBV titers of the two genotypes (P > 0.05). Independent of infection status of the hens, NDV titers were higher in LB hens than in LD hens at wpi 2 (P < 0.05), but not in following weeks (P > 0.05). Uninfected LD hens had lower AMPV titers than their infected counterparts at 6 and 14 wpi (P < 0.05). Regardless of nematode infection, LD hens revealed a higher risk of responding weak to vaccination against NDV (odds ratio = 5.45; P = 0.021) and AMPV (odds ratio = 13.99, P < 0.001) than did LB hens (P > 0.05). We conclude that nematode infections have no adverse effects on non-specific and vaccine-induced humoral immunity in either genotype. LB hens have higher levels of total immunoglobulin isotypes than LD hens. Except for IBV, vaccine-induced humoral immune responses show a dependency on genotype. Dual-purpose hens show lower responsiveness to vaccinations against NDV and AMPV, possibly due to factors associated with increased body fat reserves in this genotype.

Prioritizing smallholder animal health needs in East Africa, West Africa, and South Asia using three approaches: Literature review, expert workshops, and practitioner surveys

Managing the health needs of livestock contributes to reducing poverty and improving the livelihoods of smallholder and pastoralist livestock keepers globally. Animal health practitioners, producers, policymakers, and researchers all must prioritize how to mobilize limited resources. This study employed three approaches to prioritize animal health needs in East and West Africa and South Asia to identify diseases and syndromes that impact livestock keepers. The approaches were a) systematic literature review, b) a series of expert workshops, and c) a practitioner survey of veterinarians and para-veterinary professionals. The top constraints that emerged from all three approaches include endo/ ectoparasites, foot and mouth disease, brucellosis, peste des petits ruminants, Newcastle disease, and avian influenza. Expert workshops additionally identified contagious caprine pleuropneumonia, contagious bovine pleuropneumonia, mastitis, and reproductive disorders as constraints not emphasized in the literature review. Practitioner survey results additionally identified nutrition as a constraint for smallholder dairy and pastoralist small ruminant production. Experts attending the workshops agreed most constraints can be managed using existing veterinary technologies and best husbandry practices, which supports a shift away from focusing on individual diseases and new technologies towards addressing systemic challenges that limit access to veterinary services and inputs. Few research studies focused on incidence/ prevalence of disease and impact, suggesting better incorporation of socio-economic impact measures in future research would better represent the interests of livestock keepers.

Global and regional prevalence of helminth infection in chickens over time: a systematic review and meta-analysis

Gastrointestinal helminth parasites are a concern for the poultry industry worldwide as they can affect the health, welfare, and production performance. A systematic review of the prevalence over time in different countries may improve our understanding of gastrointestinal helminthiasis in chickens and subsequently lead to improved poultry health. The aim of this systematic review and meta-analysis was to provide an overview of the published information regarding the epidemiology and the diagnostic approaches of chicken helminth infection. Six databases were searched for studies, and a total of 2,985 articles published between 1942 and 2019 were identified and subsequently screened for eligibility using title or abstract and full text assessment, resulting in 191 publications to be used in the study. Postmortem diagnostics (73.8%) and the flotation technique (28.8%) were commonly used to detect helminth infections with a pooled prevalence of 79.4% ranging from 4 to 100%. More than 30 helminth species in chicken populations were identified including Ascaridia galli (35.9%), Heterakis gallinarum (28.5%), Capillaria spp. (5.90%), and Raillietina spp. (19.0%) being the most prevalent. The reported prevalence of helminth infection decreased over time in developing countries while it increased in the developed world. Chicken kept in backyard and free-range systems had a markedly higher pooled prevalence of helminth infection (82.6 and 84.8%, respectively) than those housed in cage production systems (63.6%). This may indicate the need for more rigorous control and prevention measures in free-range and backyard production systems using regular deworming coupled with access to early and accurate diagnosis allowing for early intervention.

Exploiting the diphtheria toxin internalization receptor enhances delivery of proteins to lysosomes for enzyme replacement therapy

Enzyme replacement therapy, in which a functional copy of an enzyme is injected either systemically or directly into the brain of affected individuals, has proven to be an effective strategy for treating certain lysosomal storage diseases. The inefficient uptake of recombinant enzymes via the mannose-6-phosphate receptor, however, prohibits the broad utility of replacement therapy. Here, to improve the efficiency and efficacy of lysosomal enzyme uptake, we exploited the strategy used by diphtheria toxin to enter into the endolysosomal network of cells by creating a chimera between the receptor-binding fragment of diphtheria toxin and the lysosomal hydrolase TPP1. We show that chimeric TPP1 binds with high affinity to target cells and is efficiently delivered into lysosomes. Further, we show superior uptake of chimeric TPP1 over TPP1 alone in brain tissue following intracerebroventricular injection in mice lacking TPP1, demonstrating the potential of this strategy for enhancing lysosomal storage disease therapy.

Viability and development of Ascaridia galli eggs recovered in artificial media followed by storage under different conditions

Eggs oviposited by Ascaridia galli females in artificial media are commonly used as a source of infective material. We investigated the rate of egg production by cultured mature females (n = 223), and changes in egg viability under different storage and incubation conditions. Eggs recovered after 1, 2 or 3 days of culture were subjected to either (1) storage in water at 4°C (1, 4 or 8 weeks) followed by incubation in 0.1 N H2SO4 at 26°C (2, 4 or 6 weeks); or (2) prolonged storage at 4°C (up to 14 weeks). Egg development and viability was assessed by morphology coupled with a viability dye exclusion test of hatched larvae. Of the 6,044 eggs recovered per mature female 49.2, 38.5 and 12.3% were recovered on days 1, 2 and 3 of worm incubation respectively with similar initial viability (≥99%) between days. Eggs recovered on different days had only minor differences in viability after storage. The prolonged storage period at 4°C significantly affected both viability and embryonation ability resulting in decline in viability of 5.7-6.2% per week. A smaller but significant decline in egg (2.0%) and hatched larval (1.4%) viability per week of incubation at 26°C was also observed. We conclude that storage and incubation conditions, not the day of egg recovery, are the main factors affecting A. galli egg viability. Our findings indicate that under aerobic conditions storage at 26°C may be preferable to 4°C whereas other studies indicate that under anaerobic conditions storage at 4°C is preferable.

The impacts of Ascaridia galli on performance, health, and immune responses of laying hens: new insights into an old problem

Gastrointestinal nematodes are re-emerging in countries where the popularity of free-range poultry production systems is increasing. Amongst all gastrointestinal nematodes, Ascaridia galli is of significant concern due to the parasite's direct life cycle and ability to survive extreme environmental conditions. In laying hens, A. galli parasites have been associated with reduced health, welfare, immunity, and egg production. Direct losses are caused by obstruction and damage of the intestinal tract in hens when high worm burdens are present. These result in reduction in egg production and body weight of infected laying hens, consequently leading to significant economic losses for farmers. Furthermore, heavy infections with A. galli may lead to increased mortality within the flock. Indirect losses are due to suppression of immune system function which can increase susceptibility to secondary infections. Infection with A. galli can also alter nutrient utilization and absorption. Levels of anti- A. galli serum and egg yolk antibodies increase following A. galli infection. Elevated antibodies can be used as an indicator of current or previous infections and therefore can be used as a diagnostic tool. The impact of A. galli on hen health and welfare manifests through the depletion of liver lipid reserves and increased use of energy reserves to mount immune responses against the parasite. This review highlights the variable effects of A. galli infection on the performance, health, egg quality, and emphasizes especially on immune responses of free-range laying hens as well as it evaluates various potential detection methods and preventive and control measures of this parasitic disease.

Molecular characterization of Raillietina isolates from the gastrointestinal tract of free range chickens (Gallus Gallus domesticus) from the southern region of Zimbabwe using the 18S rDNA gene

Parasitic diseases are among the major constraints of poultry production. The common internal parasitic infections occurring in poultry include cestodes and other gastrointestinal helminths. The aim of this study was to characterize Raillietina spp. from the gastrointestinal tract of free-range chickens using 18S rDNA genes. This was achieved through the DNA extraction from tapeworms isolated from the gastrointestinal tract of routine slaughtered free-range chickens using 18S and amplifying the partial 18S rDNA genes using PCR. A total of 34 intestine samples were collected from 9 different areas in Matabeleland region and tapeworms were isolated for microscopic examination and morphological characterization. All 34 chickens examined had tapeworms and morphological characterization confirmed those used in the study as belonging to the Raillietina group. DNA extraction was then successfully carried out for 9 cestode isolates followed by the PCR amplification of the 18S genes. The products were sequenced and 4 of the 9 isolates were positively identified using BLAST as Raillietina tunetensis and the other 5 were only identified as Raillietina spp. These sequences were then aligned with other known sequences of Raillietina isolates from GenBank and a phylogenetic tree was constructed using the neighbor-joining method and distance computed using the maximum composite method. The phylogenetic tree showed that three of the unidentified Raillietina species are in the neighboring position with Raillietina sonini whilst the other two are in the neighboring position with Raillietina tetragona. This is the first record of R. tunetensis in Gallus Gallus domesticus from Zimbabwe. This clustering on the phylogenetic tree however, did not differentiate samples according to geographical location showing that this tool can be used to infer phylogenetic data for speciation.

Virus-induced immunosuppression in turkeys (Meleagris gallopavo): A review

Immunosuppression is characterized by a dysfunction of humoral and/or cellular immune response leading to increase of susceptibility to secondary infections, increase of mortality and morbidity, poor productivity, and welfare and vaccination failures. Humoral immune response depression is due to perturbation of soluble factors, as complement and chemokines in innate immunity and antibodies or cytokines in adaptive immunity. At the cellular immune response, immunosuppression is the consequence of the dysfunction of T-cells, B-cells, heterophils, monocytes, macrophages, and natural Killer cells. Immunosuppression in turkeys can be caused by numerous, non-infectious, and infectious agents, having variable pathological and molecular mechanisms. Interactions between them are very complex. This paper reviews the common viruses inducing clinical and sub-clinical immunosuppression in turkeys, and enteric and neoplastic viruses in particular, as well as the interactions among them. The evaluation of immunosuppression is currently based on classical approach; however, new technique such as the microarray technology is being developed to investigate immunological mediator’s genes detection. Controlling of immunosuppression include, in general, biosecurity practices, maintaining appropriate breeding conditions and vaccination of breeders and their progeny. Nevertheless, few vaccines are available against immunosuppressive viruses in turkey’s industry. The development of new control strategies is reviewed.

Effect of the nematophagous fungus Pochonia chlamydosporia on soil content of ascarid eggs and infection levels in exposed hens

BACKGROUND

The nematophagous fungus Pochonia chlamydosporia can degrade ascarid (e.g. Ascaridia galli) eggs in agar and soil in vitro. However, it has not been investigated how this translates to reduced infection levels in naturally exposed chickens. We thus tested the infectivity of soil artificially contaminated with A. galli (and a few Heterakis gallinarum) eggs and treated with P. chlamydosporia. Sterilised and non-sterilised soils were used to examine any influence of natural soil biota.

METHODS

Unembryonated eggs were mixed with sterilised (S)/non-sterilised (N) soil, either treated with the fungus (F) or left as untreated controls (C) and incubated (22 °C, 35 days) to allow eggs to embryonate and fungus to grow. Egg number in soil was estimated on days 0 and 35 post-incubation. Hens were exposed to the soil (SC/SF/NC/NF) four times over 12 days by mixing soil into the feed. On day 42 post-first-exposure (p.f.e.), the hens were euthanized and parasites were recovered. Serum A. galli IgY level and ascarid eggs per gram of faeces (EPG) were examined on days -1 and 36 (IgY) or 40 p.f.e. (EPG).

RESULTS

Egg recovery in SF soil was substantially lower than in SC soil, but recovery was not significantly different between NF and NC soils. SF hens had a mean worm count of 76 whereas the other groups had means of 355-453. Early mature/mature A. galli were recovered from SF hens whereas hens in the other groups harboured mainly immature A. galli. Heterakis gallinarum counts were low overall, especially in SF. The SF post-exposure IgY response was significantly lower while EPG was significantly higher compared to the other groups.

CONCLUSIONS

Pochonia chlamydosporia was very effective in reducing ascarid egg numbers in sterilised soil and thus worm burdens in the exposed hens. However, reduced exposure of hens shifted A. galli populations toward a higher proportion of mature worms and resulted in a higher faecal egg excretion within the study period. This highlights a fundamental problem in ascarid control: if not all eggs in the farm environment are inactivated, the resulting low level infections may result in higher contamination levels with associated negative long-term consequences.

Detection of Ascaridia galli infection in free-range laying hens

Reliable methods for detection of A. galli infection using excreta egg count (EEC) and ELISA assays to determine A. galli specific IgY levels in serum and yolk samples were compared from hens infected naturally and artificially. Artificially infected hens were used to generate samples for analysis of preferred detection methods and to generate contaminated ranges for use in the naturally acquired infection study in which Lohmann Brown hens (n = 200) at 16 weeks of age were randomly assigned to four treatments with five replicate pens. Hens of negative control (NC) ranged on a decontaminated area, hens of low infection, medium infection and positive control (PC) ranged on the areas previously contaminated by hens artificially infected with 250, 1000 and 2500 A. galli eggs/hen, respectively. Additionally, hens of PC were orally infected with 1000 A. galli eggs/hen. Anti A. galli antibody levels in hen serum (SIgY) and yolk (YIgY) were measured before range access, and 2, 7 and 12 weeks after access to the contaminated ranges. In a natural infection study, eggs were detected in the excreta of all hens 4 weeks after range access, with the exception of NC in which no eggs were detected. EEC increased to reach maximum value (2204 ± 307 eggs/g) after 11 weeks of range access and then declined at 12 weeks (905 ± 307eggs/g) (p < 0.01). While SIgY OD values were not different in hens between any groups before range access, after 2 weeks, both SIgY and YIgY gradually increased in hens of PC (1.17 ± 0.03 and 0.88 ± 0.04) and medium infection (1.07 ± 0.03 and 0.96 ± 0.04) compared to low infection (0.38 ± 0.03 and 0.29 ± 0.04) (p < 0.01) and NC. After 12 weeks, SIgY were similar in hens of PC, medium and low groups whereas YIgY was higher in hens of low infection group (p < 0.01). Sensitivity of the serum and egg yolk antibody levels assay to detect A. galli infection was 100% and 96%, respectively, whereas the pooled EEC method yielded a sensitivity of 93%. The results of this study suggest that hens naturally infected with A. galli produce both SIgY and YIgY at different levels depending on the infection intensity and duration of exposure which allows the diagnosis of prior infection or early diagnosis of current infection. Use of the practical and non-invasive method of yolk sample analysis for detecting IgY can be just as informative as using serum samples to detect A. galli infection.

Cytokine gene expression profiles in chicken spleen and intestinal tissues during Ascaridia galli infection

In the poultry production industry, chickens with access to outdoor areas are exposed to a wide range of parasites e.g. the helminth Ascaridia galli. By real-time quantitative RT-PCR, the relative gene expression of the T helper 1 (Th1) cytokine IFN-γ, the T helper 2 (Th2) cytokine IL-13, the anti-inflammatory cytokines IL-10 and TGF-β4 and the pro-inflammatory cytokine IL-17F were determined over a period of 3 weeks in A. galli and non-A. galli-infected chickens. A characteristic Th2 response was observed in the jejunum of A. galli-infected chickens with increased expression of IL-13 and decreased expression of IFN-γ from day 14 post infection. At the putative time of larvae invasion into the intestinal mucosa (day 7), an increased expression of IFN-γ, IL-10, and TGF-β4 was observed in the spleen. At the putative onset of the innate immune response (day 10), a decreased expression of jejunal IFN-γ and IL-13 was observed. Finally, at the expected period of an adaptive immune response (days 14-21) a general decreased expression of IFN-γ and TGF-β4 in spleen and IFN-γ in jejunum was followed by a decreased expression of IFN-γ and IL-10 at day 21 in caecal tonsils.

Infection-interactions in Ethiopian village chickens

Chickens raised under village production systems are exposed to a wide variety of pathogens, and current or previous infections may affect their susceptibility to further infections with another parasite, and/or can alter the manifestation of each infection. It is possible that co-infections may be as important as environmental risk factors. However, in cross-sectional studies, where the timing of infection is unknown, apparent associations between infections may be observed due to parasites sharing common risk factors. This study measured antibody titres to 3 viral (Newcastle disease, Marek's disease and infectious bursal disease) and 2 bacterial (Pasteurella multocida and Salmonella) diseases, and the infection prevalence of 3 families of endo- and ecto-parasites (Ascaridida, Eimeria and lice) in 1056 village chickens from two geographically distinct populations in Ethiopia. Samples were collected during 4 cross-sectional surveys, each approximately 6 months apart. Constrained ordination, a technique for analysis of ecological community data, was used to explore this complex dataset and enabled potential relationships to be uncovered and tested despite the different measurements used for the different parasites. It was found that only a small proportion of variation in the data could be explained by the risk factors measured. Very few birds (9/1280) were found to be seropositive to Newcastle disease. Positive relationships were identified between Pasteurella and Salmonella titres; and between Marek's disease and parasitic infections, and these two groups of diseases were correlated with females and males, respectively. This may suggest differences in the way that the immune systems of male and female chickens interact with these parasites. In conclusion, we find that a number of infectious pathogens and their interactions are likely to impact village chicken health and production. Control of these infections is likely to be of importance in future development planning.

Ascaridia galli infection influences the development of both humoral and cell-mediated immunity after Newcastle Disease vaccination in chickens

Potent vaccine efficiency is crucial for disease control in both human and livestock vaccination programmes. Free range chickens and chickens with access to outdoor areas have a high risk of infection with parasites including Ascaridia galli, a gastrointestinal nematode with a potential influence on the immunological response to vaccination against other infectious diseases. The purpose of this study was to investigate whether A. galli infection influences vaccine-induced immunity to Newcastle Disease (ND) in chickens from an MHC-characterized inbred line. Chickens were experimentally infected with A. galli at 4 weeks of age or left as non-parasitized controls. At 10 and 13 weeks of age half of the chickens were ND-vaccinated and at 16 weeks of age, all chickens were challenged with a lentogenic strain of Newcastle disease virus (NDV). A. galli infection influenced both humoral and cell-mediated immune responses after ND vaccination. Thus, significantly lower NDV serum titres were found in the A. galli-infected group as compared to the non-parasitized group early after vaccination. In addition, the A. galli-infected chickens showed significantly lower frequencies of NDV-specific T cells in peripheral blood three weeks after the first ND vaccination as compared to non-parasitized chickens. Finally, A. galli significantly increased local mRNA expression of IL-4 and IL-13 and significantly decreased TGF-ß4 expression in the jejunum two weeks after infection with A. galli. At the time of vaccination (six and nine weeks after A. galli infection) the local expression in the jejunum of both IFN-? and IL-10 was significantly decreased in A. galli-infected chickens. Upon challenge with the NDV LaSota strain, viral genomes persisted in the oral cavity for a slightly longer period of time in A. galli-infected vaccinees as compared to non-parasitized vaccinees. However, more work is needed in order to determine if vaccine-induced protective immunity is impaired in A. galli-infected chickens.

A meta-analysis of observational epidemiological studies of Newcastle disease in African agro-systems, 1980-2009

Newcastle disease (ND) is one of the most important and widespread avian pests. In Africa, backyard poultry production systems are an important source of protein and cash for poor rural livelihoods. ND mortality in these production systems is important and seriously disrupts benefits derived from it. This study undertook an African continental approach of ND epidemiology in backyard poultry. After a systematic literature review of studies published from 1980 to 2009, a meta-analysis of spatio-temporal patterns of serological prevalence and outbreak occurrence was performed. Average ND serological prevalence was estimated at 0·67 [95% confidence interval (CI) 0·58-0·75] in regions characterized by humid ecosystems, high human and poultry densities and low altitudes; 0·36 (95% CI 0·30-0·41) in dry ecosystems at intermediate altitude where human and poultry densities are low and 0·27 (95% CI 0·19-0·38) in mountain ecosystems where human and poultry densities are intermediate. In terms of seasonality, ND outbreaks occur mostly during the dry seasons in Africa, when environmental conditions are likely to be harshest for backyard poultry. In addition, a phylogeographical analysis revealed the regionalization of ND virus strains, their potential to evolve towards a higher pathogenicity from the local viral pool and suggests a risk for vaccine strains to provide new wild strains. These results present for the first time a continent-wide approach to ND epidemiology in Africa. More emphasis is needed for ND management and control in rural African poultry production systems.

Effect of immunosuppression on newcastle disease virus persistence in ducks with different immune status

This study was carried out to verify the possibility that ducks are sources of Newcastle disease (ND) virus infection for chickens in mixed flocks. Immunosuppressed (IS) and non immunosuppressed (NIS) birds, at three different antibody levels (medium, low and absent) were used; the titres having been induced through vaccination, and Immunosuppression done using dexamethazone. Each of the 3 respective groups was further divided into 2 groups of about 12 ducks each: one challenged with velogenic ND virus; the other not challenged. Selected ducks from all groups had their antibody titres monitored serially using hemagglutination inhibition test, while two birds from each of the challenged groups were killed and respective tissues processed for ND viral recovery, using chicken embryo fibroblasts. In general, antibody titres of IS and NIS challenged ducks were significantly higher than their unchallenged counterparts (P < 0.05). Non-challenged pre-immunised ducks had a progressive decrease in antibody levels; non-immunised ducks did not seroconvert. Newcastle disease virus was isolated from livers and kidneys of the challenged ducks throughout the experimental period; indicating a possibility of viral excretion, especially when the birds are stressed. It, therefore, provides another possible model of viral circulation within mixed flocks.

Causes of mortality in commercial organic layers in Denmark

A longitudinal study investigated the courses of mortality in commercial free-range organic layer flocks in Denmark. In total, 15 organic egg-producing flocks from 11 farms were randomly selected among 80 farms registered in Denmark. Four farms with confined egg production on deep litter were included for comparison. Flock sizes ranged from 2260 to 5940 layers. The flocks were monitored from introduction to the layer farm until slaughter. Flock mortalities ranged from approximately 2% to 91%, with a mean of 20.8% for organic flocks compared with 7% for confined flocks on deep litter. In total, 4608 layers were submitted for postmortem examination, representing > 40% of all the dead layers in the investigated flocks. Outbreaks of erysipelas (Erysipelothrix rhusiopathiae) and fowl cholera (Pasteurella multocida) were observed in two and three organic flocks, respectively. The mortality rate reached 91% in one organic flock dually affected by erysipelas and fowl cholera. In six organic flocks, outbreaks of blackhead were diagnosed. Concurrent infections of erysipelas and blackhead were diagnosed in one organic flock. Escherichia coli infections in the form of septicemia were identified in all organic flocks. In addition, cannibalism and constipation contributed significantly to the mortality in some organic flocks. In the confined deep litter flocks, E. coli infection, constipation, and cannibalism represented the most common causes of mortality.

Local chicken production system in Malawi: household flock structure, dynamics, management and health

Household flocks of scavenging chickens were monitored from August 2002 to August 2003 in 27 villages in Lilongwe, Malawi. The objective was to evaluate the local chicken production system by investigating flock structure, utilization, management and constraints. Farmers and researchers jointly obtained data on household flocks. Mean flock size was 12.9, with a range of 1-61 chickens. The flock dynamics of chickens over 8 weeks old constituted 91% migrating out of flocks and 9% into the flocks. Primary functions based on flock dynamics were, in order of importance, household consumption, participation in socio-cultural ceremonies, selling, exchanging breeding stock and gifts. Of the flock exits, 43.9% were due to losses from diseases, predation and theft. Most flocks (85%) were housed in human dwelling units. Scavenging was the main source of feed. The majority (77.6%) of farmers supplemented their chickens erratically with energy-rich feeds, mostly maize bran. Most supplementation took place during the cold-dry season. Village chicken production offers diverse functional outputs but faces animal health (diseases, parasites, predation) and management (feeding) constraints, which require an integrated intervention approach at community and household level.

Clonal stability of Pasteurella multocida in free-range layers affected by fowl cholera

Detailed longitudinal studies of the genetic stability of Pasteurella multocida ssp. multocida, the cause of fowl cholera, have not previously been carried out. Consequently, the aim of the present study was to provide detailed information on the genetic stability and diversity of P. multocida ssp. multocida in poultry flocks over time, enabling new insights into the molecular epidemiology of this important poultry pathogen. Longitudinal investigations of the rate and causes of mortality were carried out on two free-range layer farms (A and B) over a period of 11 months. The total mortality of two flocks, A1 and A2, on farm A were 62 and 91%, respectively, while the total mortality of a single flock B1 on farm B was 6%. Postmortem examinations were performed on 708 layers from flocks A1 and A2 and in 159 from flock B1. Fowl cholera was the main cause of mortality on both farms. Pasteurella multocida isolates recovered from layers on both farms were characterized phenotypically and genotypically, and 322 isolates were identified as P. multocida ssp. multocida. The genetic diversity of 99 isolates from farm A and 31 from farm B was characterized by restriction endonuclease analysis and amplified fragment length polymorphism analysis. The isolates on each farm had a unique restriction endonuclease analysis and amplified fragment length polymorphism analysis type, suggesting a single introduction of a successful clone. Furthermore the clone on farm A was identical to clones previously isolated from outbreaks in the avifauna of Denmark in 1996 and 2001 and in Sweden in 1998. This study provides convincing evidence for the clonal stability of outbreak clones of P. multocida.

Aflatoxicosis, infectious bursal disease and immune response to Newcastle disease vaccination in rural chickens

To investigate the immunosuppressive effects of infectious bursal disease virus (IBDV) and aflatoxin in indigenous chickens of Uganda, Newcastle disease (ND) seronegative chicks were randomly allocated to two treatment groups. Group A chicks were injected intramuscularly at the age of 3 weeks every 2 days up to four times with 0.250 mg aflatoxin B1 per bird, group B was infected occulo-nasally with IBDV 3 days prior to vaccination, while group C was left as a control group. All the chicks from the three groups were then vaccinated with Hitchner B1 vaccine at 21 days of age followed by a secondary vaccination with La Sota vaccine 3 weeks later. Humoral and cell-mediated immune responses were assessed by measuring antibody levels and delayed hypersensitivity reaction post vaccination. Growth performance in the three groups was assessed by weekly body weights while evidence of excretion of vaccinal ND virus was detected by reverse transcription-polymerase chain reaction.A significant (P < 0.05) reduction in the haemagglutination inhibition of ND antibody titre following initial priming with Hitchner B1 and subsequent booster with La Sota vaccines and a delayed hypersensitivity test following sensitization with dinitrochlorobenzene showed aflatoxin to be a more potent immunosuppressant than IBDV. Aflatoxin exerted its maximum effects during primary antibody response in the second and third weeks post vaccination. Aflatoxin and IBDV did not affect growth rates (P > 0.05) but prolonged La Sota vaccine virus excretion in faeces. Under our experimental conditions, aflatoxin and IBDV do not significantly affect the immune response of rural chickens to ND vaccination.

Th1/Th2 polarization by viral and helminth infection in birds

Mammals developed an immune system able to functionally polarize into so-called type 1 or type 2 immune pathways, to resolve infections with intracellular and extracellular pathogens, respectively. In the well-studied avian immune system of the chicken, however, no evidence for polarized immunity could be found, as yet. To investigate whether these two major arms of mammalian immunity, regulated by a T helper (Th)1/Th2 cytokine balance, evolved similarly in birds, chickens were exposed to a prevalent intracellular (viral) or extracellular (helminth) infection. By using semi-quantitative RT-PCR analysis we provide evidence that polarization of Th1/Th2 type immunity extends beyond mammalian species, and, therefore, has been evolutionary conserved for more than 300 million years, when the lineages of mammalian and avian vertebrates are assumed to have segregated.